Editorial: Post-fire impacts on watershed water quality and hydrology

1 Introduction

The increasing occurrence, intensity, and severity of wildfires represent major environmental and societal challenges, shaped by interactions among land use, fuel availability, ignition patterns, and climate conditions that favor more frequent and extreme fire weather (Jolly et al., 2015; Andela et al., 2019; Cunningham et al., 2025). Although wildfires are often associated with their immediate and visible consequences, including losses of vegetation, habitat, infrastructure, and human life, their effects can extend beyond burned areas and persist long after the flames are extinguished.

Wildfires are increasingly recognized as major disturbances to watershed functioning, with implications for downstream environments and water resources (Shakesby and Doerr, 2006; Smith et al., 2011). Post-fire changes in soils, vegetation cover, infiltration, runoff, and erosion can mobilize sediments, ash, nutrients, organic matter, metals, and other contaminants into rivers, reservoirs, lakes, and coastal waters (McGuire et al., 2024; Vieira et al., 2026). These off-site impacts can compromise aquatic ecosystems, degrade drinking-water sources, affect reservoir operation, and create risks for human and animal health (Hohner et al., 2019). Understanding these cascading effects is essential for improving post-fire monitoring, risk assessment, watershed management, and water-resource protection in increasingly fire-prone regions.

2 An overview of the Research Topic

Although processes such as increased runoff, erosion, sediment delivery, and nutrient export are well documented, important knowledge gaps remain, particularly regarding how post-fire disturbances alter the sources, transport, transformation, and persistence of water-quality constituents across watersheds and downstream receiving waters. This Research Topic brings together contributions that examine multiple pathways through which wildfires affect water quality, including carbon mobilization, ecosystem responses, contaminant transport, monitoring needs, and the downstream propagation of nutrients and metals.

At the coastal interface, Laicher-Edwards et al. examine dissolved black carbon dynamics in estuaries affected by the 2019–2020 Australian bushfires. Their study highlights the role of estuaries as transitional environments within the land–ocean aquatic continuum, where fire-derived carbon may be processed or attenuated before reaching the ocean.

At the stream ecosystem scale, Reale et al. investigate wildfire effects on water quality and gross primary production in two adjacent montane watersheds affected by the Las Conchas wildfire in New Mexico. Their findings show increases in turbidity and specific conductance after the fire, followed by gradual recovery toward pre-fire conditions, while also revealing variability in ecological responses between similarly burned watersheds.

From a community water resilience perspective, Newcomer et al. draw on five wildfire case studies in the United States to show how rapid-response research can support decision-making before, during, and after wildfire events. Their contribution emphasizes the value of collaboration among scientists, water agencies, and managers, and points to the need for more proactive approaches, including pre-fire data collection, coordination exercises, and research-to-operations frameworks.

The Research Topic also draws attention to emerging risks that remain insufficiently understood. Through a scoping review, Fitzhugh and Mateus explore wildfire-driven erosion as a potential pathway for the mobilization of endocrine disrupting chemicals into watersheds. Their analysis identifies a notable gap in current knowledge, particularly regarding the transport and fate of these contaminants in aquatic environments after fire.

The importance of high-frequency monitoring is demonstrated by Tunby et al., who analyze water quality behavior following the Hermit's Peak–Calf Canyon wildfire in New Mexico. Using in-situ sensors across a large fluvial network, the study shows that acute impacts were strongest near the burned area, where storm-driven turbidity peaks and dissolved oxygen declines reached levels that could be missed by conventional discrete sampling.

Finally, Kaphle et al. extend this watershed-scale perspective by assessing the propagation of nutrients and metals after the Hermit's Peak–Calf Canyon gigafire. Their longitudinal analysis shows that wildfire-related disturbances can travel hundreds of kilometers downstream, with substantial increases in nutrient concentrations and exceedances of background levels and health-related thresholds for some trace metals.

Collectively, these studies provide a present overview of current research and emphasize both the progress made and the remaining challenges in understanding, monitoring, and mitigating wildfire impacts on water quality.

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Footnotes

Edited and reviewed by: Boris M. Van Breukelen, Delft University of Technology, Netherlands